1. Field of the Invention
The present invention relates to cryopumps, and more particularly, to cryosorption pumps for use in fusion reaction systems wherein the pump is provided with a physical barrier.
2. Discussion of the Prior Art
Cryosorption pumps for use in fusion reaction systems are known in the art, and encompass such types of pumps with or without the incorporation of physical barriers. The pumps which include physical barriers have provisions for regeneration and generally separate helium from isotopes of hydrogen by providing a sorbent surface for capturing the helium molecules while condensing the hydrogen isotopes onto a second surface. Regeneration takes place by simultaneously warming both surfaces and using a separate rough pumping system to pump out the sorbed gases.
The physical barriers of the prior art pumps separate the surfaces from each other during regeneration, but the separation is incomplete under high pressure conditions, such as upon the occurrence of a system failure or line rupture. The hydrogen isotopes, namely deuterium and tritium, may escape the condensing surface and reach the sorbent surface, the latter of which is generally charcoal, but may also include zeolite, and other gas impurities may also reach the sorbent surface. The cryopump design must allow for rapid venting of the cryogens in the event of any inadvertent warming which would result in the event of such a failure. Rapid venting may be accomplished by several methods, such as through the utilization of relief valves, burst discs, and appropriately sized vent lines.
Furthermore, prior art cryopumps with physical barriers generally do not overcome the problem of bypass flow of incoming gases that escape the condensing surface during normal operation of the pump which allows hydrogen isotopes to bypass that surface and reach the sorbent surface. The barriers are generally removed from the area where sorption takes place and do not participate in the normal operation of the pump.